Organic light-emitting diode (OLED) display device has been considered as a next-generation display technology due to its advantages over a liquid crystal display, such as self-luminescence, rapid response, wide viewing angle, high brightness, vivid colors, light weight and thinness.
As a main structure of the OLED display device, an OLED display substrate includes a plurality of pixel regions defined by a pixel definition layer, and each pixel region includes an OLED that emits a ray in a specific color, respectively. During the manufacture of the OLED display substrate, films of the OLED are mainly formed by an evaporation or solution process. The evaporation process has been widely used for the manufacture of a small-size display device. The solution process mainly includes inkjet printing, spaying, spinning, and screen printing. Due to a high material utilization rate and being applicable to a large-size product, the inkjet printing technique has been considered as an important way for the mass production of the large-size OLED display device.
In order to improve the production efficiency, a sprayer of an inkjet printing device includes a plurality of nozzles, so as to form a plurality of display layers (e.g., an organic light-emitting layer) at pixel regions in an identical color. However, during the actual manufacture, it is impossible to fully ensure an even ink amount from the respective nozzles. Prior to the inkjet printing, it is required to precisely adjust the ink amount for each nozzle, so that an error among ink volumes from the nozzles in unit time is less than ±0.3%. When a larger error occurs, it is able for human's eyes to distinguish between pixels due to brightness differences caused by this error after the display device is lightened up. Hence, one of the core techniques for inkjet printing lies in how to provide an even inkjet amount for the pixels.
As shown in FIG. 1, pixel regions are arranged in a matrix form in the related art, and each pixel region is usually of a strip-like shape (e.g., a red pixel region 2, a red pixel region 3 and a blue pixel region 4). Currently, each sprayer 13 from a manufacturer is usually provided with 256 or 512 nozzles 1. Hence, for the mass production of a TV with a resolution of 3840*2160, when the sprayer 13 with 256 nozzles 1 is adopted, 5 sprayers 13 are required so as to print the 3840 display layers in an identical row and at pixel regions in an identical color, and then the 5 sprayers 13 are required to be moved simultaneously in a direction as shown by an arrow in FIG. 1 so as to print the OLEDs in an identical color in all of the rows. Usually, it takes 3 to 5 hours to control a volume error for 256 nozzles 1 to be less than 0.3%, so it will take a very long time period to control the volume error for 1280 nozzles 1 to be less than 0.3%. In addition, after a certain period of time, it is required to re-adjust the ink volumes from the 1280 nozzles 1 at the expense of a lot of time and ink. In FIG. 1, different grayscales represent different thicknesses of the display layers in the red pixel units 2.